ANS:A - pitot tube

The speed of a submarine in deep sea and that of an aeroplane is typically measured by a/an pitot tube. A pitot tube is a device used to measure the velocity of a fluid flow, typically air or water. It works on the principle of Bernoulli's equation, which relates the pressure and velocity of a fluid in motion. In the case of an aeroplane, a pitot tube is mounted on the exterior of the aircraft, usually on the wing or fuselage, to measure the airspeed or the velocity of the aircraft relative to the surrounding air. The pitot tube has one opening facing into the airflow and another opening perpendicular to the flow direction. The pressure difference between these two openings is used to determine the airspeed. Similarly, in the case of a submarine, a pitot tube can be used to measure the velocity of the submarine through water. By sensing the pressure difference between the front-facing opening of the pitot tube and the surrounding water, the speed of the submarine can be determined. Therefore, a pitot tube is the appropriate device for measuring the speed of both a submarine in deep sea and an aeroplane.